Technologies of measuring locations for provision of Location-based Services (LSB) are divided into a network-based method of determining locations according to software using a propagation environment which is the cell radius of the base transceiver station of a mobile communication network in order to measure the location of a mobile terminal, a handset-based method using a Global Positioning System (GPS) receiver mounted in a mobile terminal and a hybrid method in which the above-described two methods are mixed.
The handset-based methods include an Assisted GPS (A-GPS) method and an Enhanced Observed Time Difference (E-OTD) method.
The A-GPS is a method available in both European GSM-based network technology using a TDMA radio access method and IS-95-based network technology using a CDMA radio access method. In the CDMA radio access method, the location of a mobile terminal is determined using the transmission and reception of messages via an IS-801-1 interface between the mobile terminal having a GPS receiver and the PED of a CDMA network. In this case, the number of signals received from GPS satellites is 4 or more, so that the location determination is very accurate. A-GPS includes a PDE for receiving the satellite signals received by the mobile terminal and calculating the location thereof and a mobile positioning center (MPC) for performing calculation using information about base transceiver stations within a mobile communication network or linking it to another system.
E-OTD (enhanced observed time difference) method has been standardized by a GSM standard committee for a European TDMA-based GSM method through LCS Release 98 and 99. A mobile terminal calculates relative arrival times and the difference between distances-based on signals received from three or more base transceiver stations and then determines a location. The E-OTD method mixes an OTD (observed time difference) method, an RTD (real time difference) method, and a GTD (geometric time difference) method and uses a mixture of the methods. The OTD method calculates the arrival times of signals from two base transceiver stations to a mobile terminal, and the RTD method calculates the distance between transmission start times of signals from two base transceiver stations. Furthermore, the GTD method calculates the distances between two base transceiver stations and a terminal and then calculates the difference between the distances for two base transceiver stations.
The network-based location measurement technology delivers data (PPM, OTD, etc.) measured by a terminal-based on protocols (IS-801, RRLP, RRC, etc.) agreed between a mobile terminal and a server to a location measurement server, and the location measurement server performs a function of measuring the location of the corresponding mobile terminal using the measured data (PPM, OTD, etc.). The location measurement server performs network-based location measurement (method of measuring the location of a terminal requesting location measurement by a server except for a method of measuring location using GPS satellites), and transmits the results thereof to a requester (MPC, CP (Contents Provider) or a terminal requesting a service) requesting location measurement.
Such a network-based location measurement technology includes a cell ID method using the radius cell of a base transceiver station, an angle of arrival (AOA) method of calculating locations by calculating the Line Of Bearing (LOB) in a base transceiver station while the base transceiver station receives signals transmitted from a mobile terminal, a TOA (time of arrival) method of calculating locations in a mobile terminal using the arrival time of radio waves emitted from three or more base transceiver stations, and a TDOA (time difference of arrival) method of determining a point at which two hyperbolas, which are acquired by measuring the difference between the arrival times of pilot signals received from three base transceiver stations in a mobile terminal and calculating the distance difference between base transceiver stations, intersect as the location of a mobile terminal.
Using such a conventional network-based location measurement method using has the following problems.
First, when trilateration is performed using time and distance measurement data which are parameters measured by a mobile terminal or a mobile communication network, or the intersection point of hyperbolas is calculated, the relay has a great influence. That is, upon use of the relay, the time and distance data between a base transceiver station and a terminal measured by the terminal is delayed compared to the original data, so that there is a problem in that the accuracy of location measurement is reduced.
Second, since the latitude and longitude data of a base transceiver station is not reflected immediately upon the rearrangement of the base transceiver station, so that there is a problem in that considerable error is caused in the accuracy of the latitude and longitude data referred in principal.
Third, since characteristics are different depending on network-based location measurement technologies or base transceiver stations and sectors, considerable human and physical resources are required in a process of optimizing parameters used differently for base transceiver stations and sectors to increase the accuracy of location measurement, so that there is a problem in that commercialization is different.
Therefore, conventional network-based location measurement technology uses a location measurement method having considerable problems in which errors of up to hundreds of m˜several Km occur depending on whether there is a relay, or whether optimization is completed.